function Person(name,age) {
    this.name = name;
    this.age = age ;
}
Person.prototype.sayHi = function() {
    console.log('hello');
}
const yj = {};//空的字面量
//call 可以手动指定函数内部this
Person.call(yj,'袁静',18)
console.log(yj);
yj.__proto__= Person.prototype
yj.sayHi();
console.log(yj);